For the first time in more than a century, a woman is coming to a U.S. currency bill, the Treasury Department announced Wednesday.

In a process that has been "years in the making," the government will unveil the new $10 bill in 2020, and it will include a famous female face, Treasury Secretary Jack Lew said on a call with reporters. The department has not yet decided which woman will grace the new bill, he said, but the eventual choice will hold global significance.

"With such a wide reach, America's currency makes a statement about who we are and what we stand for as a nation," Lew said, adding that "this decision of putting a woman on the $10 bill reflects our aspirations for the future as much as a reflection of the past."

Some have called for a woman to replace Andrew Jackson on the $20 bill, but Lew said that note was not yet up for a redesign. One group, Woman on 20s, announced in May that abolitionist Harriet Tubman had won its campaign to be the new face of that bill.

This won't be the first time a woman was on U.S. currency: Martha Washington and Pocahontas both had places on bills in the 1800s. Still, the new $10 note will be the first to feature a woman in more than 100 years, Lew said.

The current $10 bill features Alexander Hamilton, and fans of the founding father need not worry about his outright disappearance. The Treasury will "definitely" continue to include his image in some way on the new notes, Lew said—whether that be on the same bill as the as-yet-undecided woman, or on a different bill.

"It was personally very important to me to make sure that as we make this decision we continue to honor Alexander Hamilton, who played such a formative role in the creation of our country, the establishment of democracy as we know it, and the principle of the soundness of our currency," Lew said.

In fact, the range of options remains fairly unrestricted, the treasury secretary said, explaining that his department could even opt to include more than one woman.

The Treasury said in 2013 that it had selected the $10 bill for the next redesign, and the department announced that the new note will be the first of the next democracy-themed generation of currency. This means that Lew plans to select a woman "who was a champion for our inclusive democracy," according to a release from the Treasury.

Lew said the 2020 unveiling of the new $10 will help mark the 100th anniversary of the passage of the 19th Amendment, which gave women the vote.

Recent new bills have had themes: Beginning in 2003, the theme of "freedom" has been seen in the $10's depiction of Statue of Liberty's torch, the $20's large eagle, and the $100's images of the Declaration of Independence, the Treasury said.

In order to help develop ideas for the new $10 bill's design, and even the subject of its portrait, the Treasury is soliciting comments from the public through the website thenew10.treasury.gov or by using the hashtag "#TheNew10" on social media.

Lew said his department will review the suggestions over the summer, and he expects to announce a decision on whom the bill will depict later this year.

The only statutory criterion for a U.S. currency portrait is that the person must be deceased, Lew said.